There has been much conceptual work proposing that there are developing interrelations between cognition and emotion during very early childhood, as well as the suggestion that cognition and emotion are fully integrated by school age. There are, however, few empirical data on cognition-emotion development. This application describes a longitudinal study designed to investigate the integrative development of cognition and emotion during infancy and early childhood. The unique feature of this study is that it grounds cognition-emotion relations within a psychobiological theoretical framework, thus focusing on physiological as well as behavioral indices of this integration. We propose that the neural mechanisms and resulting regulatory skills associated with developing temperament-related attentional control are critical for defining the trajectories of both cognitive and emotional development. An innovative feature of this study is the incorporation of maternal behaviors into the examination of emerging cognition-emotion relations. This proposed study has five assessment points (5, 10 months;2, 3, 4 years) and has the potential to make a significant contribution to the study of early development across the transition from infancy through early childhood. First, it will make a significant contribution to our knowledge of the development of working memory, emotion regulation, and attentional control in early development by providing longitudinal data on the trajectories of these three developmental processes. Second, it will allow for examination of emerging cognition-emotion relations and the hypothesized role of attentional control to impact the development of both working memory and emotion regulation. Third, it will provide information on the contributions of child temperament and parenting on the developmental trajectories of working memory, attentional control, and emotion regulation. Innovation lies in the multiple behavioral and physiological (EEG, ECG) measures used to assess the constructs of working memory, attentional control, and emotion regulation. The design and conceptual framework make this proposal novel and critical for understanding mental health development. We must understand how cognition-emotion interaction typically develops before we can begin to examine how this integration might go astray in some children, leading to extremes in self-regulation associated with problems in mental health and associated complexities in cognitive processing and school performance.